This will a bit absurd since I'm just about to turn 21!
For the last few months, I've had a constant nagging feeling that time is running out, life is too short, life will be over in a blink of an eye, etc etc. Is this similar to health anxiety?
Before I was very comfortable and viewed 30 as 'young' and late 30's/early 40's as the best time in life. However, it seems 'time' in general seems to be running out by then.
I'm about to retrain and take a huge pay cut, I'll become a student. I won't be qualified until 4 years from now. It all seems like I should've enjoyed this all sooner.
I'm proud of what I've achieved in a ridiculously short amount of time. I left school at 16 (not entirely my fault but still a regret), now earn a very good salary at 20. I am soon to celebrate my 2nd wedding anniversary, I have a wonderful, clever and beautiful DC, etc etc. But it all seems too jammed and then not jammed enough. Yet, I don't regret things because quite simply, I'm proud of who I am today and what I have achieved. Goodness knows what I'm on about with all this back and forth 
However, the bottom line is I feel a nagging sense of 'you're running out of time'. Not time for life, but time to enjoy my golden youth. I feel I have perhaps waisted a lot of these precious years not being careless enough.
I'm frequently worrying about deaths - In particular that of my Grandmother. There is nothing wrong with her, she's just getting older. I find this incredibly unsettling. I worry about my DH, I know one day he could very possibly go first and I'll be left in utter heartbreak. My soulmate would've disappeared before me.
Are these feelings normal? Should I speak to someone? I appreciate that I'm probably making very little sense. I often feel like my mind is running at a hundred miles per hour 